With recent developments in weapons technology combined with an evolving face of global terrorism, there has been an increase in the threat posed to aircraft in combat, rescue and humanitarian missions. In particular, terrorist militiamen are using inexpensive, portable and readily available weapons such as sniper rifles and shoulder-fired missiles against low flying aircraft such as helicopters, and airplanes during landing and takeoff. Many military aircraft have systems on board to identify approaching surface-to-air or air-to-air missiles and can defend themselves by deploying appropriate countermeasures.
However, sniper rifles pose larger problems to civilian aircraft as well as conventional on-board defense systems on military aircraft. These weapons tend to be lightweight and require little or no training to operate. Moreover, the bullets from these weapons are much smaller than conventional missiles. Consequently, they are difficult to detect using conventional on-board missile defense systems. Additionally, these weapons are difficult to counter because they are portable. There could be any number of armed individuals moving from one place to another firing at overhead aircraft. Therefore, target aircraft would need to not only deploy counter measures, but also identify and neutralize the source of the gunfire.
Many current-day systems for determining the location of a shooter include sensors that record acoustic signals generated by the muzzle blast of the firing weapon or by both muzzle blast as well the shockwave of the projectile. Typically requiring the signals from the muzzle blast, these systems identify the source of the projectile, the fuselage of an aircraft, however, is generally very noisy and, more importantly, noisy at muzzle-blast frequencies. Therefore, these systems are not effective in an aircraft environment, especially on the body of a plane or helicopter.
There are also systems that detect shooter locations using only acoustic signals from the shockwave of the projectile. Such systems typically include an array of closely spaced sensors. These systems are designed for ground applications, where surface gunfire typically comes from sources that are near their targets and missing projectiles fly close to the target. However, when implemented in aircraft these systems have relatively low accuracy because the aircraft are much further away from the source of gunfire and missing projectiles may fly far away from the aircraft. Furthermore, current airborne shooter detection systems have relatively low accuracy because of the influence of aircraft fluids, dust, airborne particulate matter, vibrational disturbances on an aircraft fuselage and other noise sources on the acoustic sensors themselves.
Accordingly, there is a need for a durable airborne shooter detection system capable of locating a position of a shooter.